Process for production of polyester-polyolefin film laminates

Abstract

A process for the production of a permanently bonded polyester-polyolefin film laminate is disclosed herein. The process involves exposing the surface of polyester or polyolefin film to contact with a flame so as to prime the surface thereof and thereafter coating the primed surface of the film with a layer of a molten polyolefin or polyester, respectively. Flame priming of the polyester or polyolefin film results in a permanent surface modification of the film. Thus, the time lapse between the priming of the polyester or polyolefin film and the subsequent coating with the molten polymer may be a matter of days, if desired. Multi-layer laminates which comprise a substrate-polyester-polyolefin laminate, e.g., paperboard-polyester-polyolefin laminates, can be provided by the process of the present invention by providing a previously formed laminate of a substrate and a polyester film and flame priming the polyester surface of the laminate. Thereafter, a layer of a molten polyolefin is coated onto the primed polyester surface.

What is claimed is: 
     
       1. A process for producing a permanently bonded laminate comprising polyester and polyolefin layers which consists essentially of: (A) providing a preformed polyester or a heat-sealable polyolefin film;   (B) contacting a surface of said film with the secondary portion of a flame in the vicinity of the termination of the primary portion of the flame, said flame being produced from a combustible hydrocarbon-oxygen mixture and having a temperature in the range of about 1700° F. to about 1900° F., so as to prime the surface of the film;   (C) storing the primed film; and   (D) coating the stored film with a layer of molten polymer, said molten polymer being a heat-sealable polyolefin when the film is a polyester film and a polyester when the film is a polyolefin.   
     
     
       2. The process of claim 1, wherein said film is a polyester film. 
     
     
       3. The process of claim 2, wherein said polyester is polyethylene terephthalate. 
     
     
       4. The process of claim 3, wherein said molten polyolefin comprises polyethylene. 
     
     
       5. The process of claim 2, wherein the polyester film is a lamina of paperboard-polyester laminate. 
     
     
       6. The process of claim 5 wherein said polyolefin comprises polypropylene. 
     
     
       7. A process for producing a permanently bonded laminate comprising polyester and polyolefin layers which consists essentially of: (A) providing a preformed polyester film;   (B) contacting a surface of said film with the secondary portion of a flame in the vicinity of the termination of the primary portion of the flame, said flame being produced from a combustible hydrocarbon-oxygen mixture and having a temperature in the range of about 1700° F. to about 1900° F., at least for a time sufficient to prime said surface of the film but for a time less than that which will cause substantial deformation of the film, whereby said film need not be in contact with a cooling roller when contacted by the flame; and   (C) coating the primed surface of the film with a layer of molten polymer, said molten polymer being a heat-sealable polyolefin.   
     
     
       8. The process of claim 7 wherein the film is passed over the flame at a speed of about 800 feet per minute.